From the Guidelines
Checking prolactin levels before starting testosterone replacement therapy (TRT) is necessary to rule out underlying hyperprolactinemia, which can suppress testosterone production and cause similar symptoms to low testosterone, as recommended by the American Urological Association guideline 1. This is crucial because elevated prolactin levels can indicate the presence of pituitary tumors, such as prolactinomas, which require different treatment. According to the guideline, serum prolactin should be measured in patients who have low total testosterone and low or low/normal LH levels to screen for hyperprolactinemia 1. If patients have elevated prolactin levels, prolactin measurement should be repeated to ensure that the initial elevation was not spurious, and persistently elevated prolactin levels can indicate the presence of pituitary tumors, such as prolactinomas, which require referral to an endocrinologist for further evaluation 1. Additionally, certain medications, kidney disease, hypothyroidism, and stress can also cause elevated prolactin levels, all of which require specific management rather than TRT. Proper diagnosis ensures patients receive appropriate treatment targeting the true cause of their symptoms. It is also worth noting that the American College of Physicians recommends measuring fasting morning concentrations of total testosterone on 2 occasions to diagnose hypogonadism, but does not specifically address the importance of checking prolactin levels before starting TRT 1. However, the most recent and highest quality study, the American Urological Association guideline, emphasizes the importance of checking prolactin levels before starting TRT 1.
Some key points to consider when checking prolactin levels before starting TRT include:
- Measuring serum prolactin in patients with low total testosterone and low or low/normal LH levels to screen for hyperprolactinemia 1
- Repeating prolactin measurement if initial levels are elevated to ensure that the elevation is not spurious 1
- Referring patients with persistently elevated prolactin levels to an endocrinologist for further evaluation 1
- Considering other causes of elevated prolactin levels, such as certain medications, kidney disease, hypothyroidism, and stress, and managing them accordingly 1
From the Research
Importance of Checking Prolactin Levels Before Starting Testosterone Replacement Therapy (TRT)
- Prolactin levels should be checked before starting TRT because testosterone replacement may stimulate hyperprolactinemia, as seen in a study where a patient's prolactin levels rose after initiation of testosterone replacement 2.
- Hyperprolactinemia can be caused by various factors, including pituitary tumors, and can lead to hypogonadism, which may be treated with TRT 3.
- In some cases, patients with prolactinomas may experience an increase in prolactin levels during TRT, which can be managed with aromatase inhibitors, as shown in a retrospective cohort study 4.
Potential Consequences of Not Checking Prolactin Levels
- Failure to check prolactin levels before starting TRT may lead to worsening of hyperprolactinemia, potentially causing further hypogonadism and other complications 5.
- Uncontrolled hyperprolactinemia can also lead to an increased risk of osteoporosis, infertility, and other long-term complications 3.
Management of Prolactinomas and TRT
- Dopamine agonists, such as cabergoline, are commonly used to treat prolactinomas and can help reduce prolactin levels and tumor size 2, 3.
- Testosterone replacement therapy can be used to treat hypogonadism in patients with prolactinomas, but should be done under close monitoring of prolactin levels 4, 6.
- Aromatase inhibitors may be used as an adjunct therapy to manage increased prolactin levels during TRT in patients with resistant prolactinomas 4.